The invention relates to a composite material construction. In particular, the invention relates to a method of joining pieces of material so as to form a composite material and to a composite material made by such a method primarily for use in aircraft construction.
It is known to produce wing skins from composite laminae formed from multi-axial fibres such as non-crimp or warp knitted fabric. Such skins are produced by laying several layers of fabric into a stack of required thickness. The term xe2x80x9cMulti-axialxe2x80x9d means that alternate layers of fibre will be constructed in several different directions to produce a fabric with optimum strength in required directions. Commonly used directions for wing skin manufacture are 0xc2x0 (spanwise for the wing) +45xc2x0, xe2x88x9245xc2x0 and 90xc2x0 (substantially chordwise). An example of such a skin is described in out Patent Application EP-A-0 826 488 where the +45xc2x0 and xe2x88x9245xc2x0 plies form an overlap on the 90xc2x0 plies. Normally the 0xc2x0 plies are warp dominated and the remaining plies weft dominated. The term xe2x80x9cNon-crimpxe2x80x9d refers to fabrics where warp and weft dominated fibres are laid one upon the other in non-woven fashion up to a required thickness. The fiber layers are then interconnected by a warp knitting process.
Where a multi-axial composite material is to be produced, utilising non-crimp fabrics, current machines can construct fabrics containing multi-axial layers only up to a width of 1.72 m. Structures wider than 1.72 m require two or more pieces of such fabric to be joined together using a joint for the xc2x145xc2x0 layers. An overlap joint fulfilling such a requirement is described in the above patent application.
The present application is concerned with a composite material construction involving the joining of material with alternative forms of joints in which the disruption to component thickness is minimised.
According to a first aspect of the invention there is provided a method of constructing a composite material which comprises a laminate of plies comprising warp dominated and weft dominated plies, the method being characterised by including arranging first and second pieces of material for use in the construction alongside each other with a recess being defined at least partly by a warp dominated or other ply, and arranging at least part of one of said first and second pieces of material in said recess so as to form lap joint with part of the other of the first and second pieces of material, the said parts of said first and second pieces of material including weft dominated plies.
By allowing part of one of the first and second pieces of material to be received in the recess, the disruption to component thickness resulting from the joint is minimised.
In one embodiment, each of the first and second pieces of material comprises a laminate of plies comprising a warp dominated ply and a weft dominated ply, the method including arranging the two pieces of material alongside each other with edges of the warp dominated ply of each piece extending in the same direction and with the weft dominated plies forming the lap joint. With such a method, the warp dominated ply forms part of the pieces of material to be joined together enabling a wide composite material to be built up from smaller sections of composite material.
With the arrangement disclosed in the immediate proceeding paragraph, the method may include forming the recess in an edge of the first said piece of composite material.
The corresponding edge of the second piece of composite material may be formed in the same way. The method may include forming the recess by setting one set edge of the warp dominated ply of the first piece back from an adjacent edge of the weft dominated ply forming part of the lap joint. Such an arrangement will provide a particularly simple way of defining the recess.
Where the recess is formed in an edge of the first piece of composite material, the method may include reducing the thickness of the warp dominated ply of the second piece of material adjacent its said edge to enable the weft dominated ply and a remainder part of the warp dominated ply to enter the recess when forming the lap joint. The method may include forming the corresponding edge of the first piece of the material in the same way.
The method may include bringing an edge of the remainder part of the warp dominated ply of the second piece into abutment with the edge of the warp dominated ply of the first piece when forming the lap joint.
In another embodiment, the method may include forming the recess by providing or forming between the edges of warp dominated plies or within a width of a warp dominated ply a length of thinner warp dominated material. In either case, the length of the thinner warp dominated material is preferably formed from higher filament count or higher modulus fibres compared to fibres used to construct the warp dominated plies. The lap joint may be formed so that part of the weft dominated ply of only one of the pieces lies in the recess with part of the other weft dominated ply of the other piece overlapping at least a portion of it.
The method may include placing a layer of warp dominated material on the outside of a lap joint. By doing that, it is possible to compensate for any reduction in strength which may arise due to the use of the thinner warp dominated material.
In a further embodiment, the method may include forming the recess as a groove in one surface of the warp dominated ply and providing a further weft dominated ply on the opposite surface of the warp dominated ply. The recess may be formed in, for example, a centre section of the warp dominated ply although it may be formed at other positions.
Conveniently, two pieces of material to be joined together may be fed to a machine so as to form the lap joint, the warp dominated ply and the further weft dominated ply as a single laying-up operation. As will be appreciated, such a method forms a convenient way of joining together the pieces of material by machine. Moreover, the method enables a machine previously used for bi-axial laying-up to be used to produce a multi-axial composite material much wider than would be possible on normal multi-axial laying-up machines.
With any of the foregoing embodiments in accordance with the invention, it is possible to form two layers of the jointed material with one layer inverted relative to the other with the weft dominated plies forming outer surfaces of the two layers.
Alternatively, the inversion can take place so that the warp dominated plies form the outer surfaces of the two layers.
According to a second aspect of the invention, there is provided an aerofoil having a skin formed from materials joined by the method according to the first aspect of the invention or any of the consistory clauses relating thereto.
According to a third aspect of the invention, there is provided an aircraft skin panel formed from material joined by the method according the first aspect of the invention or any of the consistory clauses relating thereto.
According to a fourth aspect of the invention there is provided a method of constructing a composite material which comprises a laminate of plies comprising a warp dominated ply and a weft dominated ply, the method including arranging first and second pieces of material for use in the construction alongside each other so that parts thereof form a lap joint which is received at least partly in a recess formed in or by a warp dominated or other ply, the said parts of said first and second pieces of material including weft dominated plies.
According to a fifth aspect of the invention there is provided a composite material construction which comprises a laminate of plies comprising warp dominated and weft dominated plies, characterised in that the construction comprises first and second pieces of material arranged alongside each other, a recess being defined at least partly by a warp dominated or other ply, part of one of said pieces of material being received in the recess and forming a lap joint with a part of the other piece of material, the said parts of the first and second pieces of material including weft dominated plies.
According to a sixth aspect of the invention there is provided a composite material construction which comprises a laminate of plies comprising a warp dominated ply and a weft dominated ply, a recess being defined at least partly by the warp dominated ply and parts of the weft dominated ply being arranged alongside each other so as to form a lap joint at least part of which is received in the recess.
The material used in the composite material construction may have the features of the material set out in the first aspect of the invention or any consistory clause relating thereto.